Lubricating composition



Patented Jan. 18, 1949 2,459,71 I LUBRICATING COMPOSITION Emmett R. Barnum and icy, (lalifl, Company,

of Delaware N Drawing.

San Francis Application January 25, 1946, Serial No. 643,461

George-L. Perry, Berkeassignors to -Shell Development co -Calif a corporation 3 Claims. (01. 2521 485) This inventionrelates to lubricating composiif:

tions, and more particularly to such compositions comprising a major proportion of amineral oil and a minor proportion'of a wear-reducing agent. "Ifhe invention relates also to an antiwear agent fo ilubiricating oils'and the process 'of preparing V.

It is customary to alter the characteristics of theusual mineraloil fractions of petroleum hydroca'rbons employed for lubricating purposes, by incorporating therein various substances or addia e-seamen of enhancing such properties of the oil as stability to oxidation, anticorrosivity, nonemuls ibility', and the like. However, precaution must be taken in such practice since it is the rule rather than the exception to it that the addition of a substance to the oil to improve it in some one respect vusually produces an undesirable result in one or. more other respects. Thus, an attempt to improve the antiwear characteristics of a. lubricant by incorporating a usual extreme pressure E. P.) agent therein, may decrease the oxidation stability of the lubricant, may produce a corrosive lubricant, and/or may increase the tendency for emulsification which is particularly undesirable in turbineoils, etc. For example, organic chlorides which have been used extensively as extreme pressure agents in lubricants are both emulsifying agents and are corrosive. Certain organic phosphorus compounds which are employed in extreme pressure lubricants also possess bothof these disadvantages. some sulfur-containing E. P. agents possess similar undesirable characteristics. Thus, alpha mercapto stearic acid increases emulsification and decreases oxida tion stability, while sulfurized sperm oil increases emulsification and decreases film 0J1 It has been known 'that'sulfurized products of derivatives .of unsaturated, fatty acids, such as their esters as for example in sperm oil, cottonseed oil, etc., impart extreme pressure" characteristics to lubricants when incorporated therein in amounts greater than 0.1%, andpreferably 1% or more. However, such substances are without any substantial effect upon the wear characteristicsof lubricants incorporating them in amounts less than 0.1 by weight. Also, it has been known that sulfurized oleic acid, as prepared by the usual process employed for the preparation of sulfurized fatty oils, is too corrosive for use in lubricants in amounts commonly employed for imparting satisfactory extreme pressure characteristics' tO-thfi lubricant. z

:::=It isan: object of the present invention to Ipro-.

tenacity of the I vide an organic lubricant having improved antiwear properties but without emulsion formin Or other deleterious properties. It is another object to provide a mineral oil composition having proprerties which render it especially suitable for use as alubricant-in turbines and similar mechanisms. Still another object is to provide abase substance which may beincorporated in mineral oil compositions to impart desirable antiwear characteristics to them, but which do not impart undesirable properties to such oil compositions.

Now, in accordance with the present invention it has been found that an improved organic lubricant composition can be prepared byincorporating in a suitable lubricating oil base a minor amount of an oil-soluble, liquid-sulfurized product of oleic acid, said sulfurized product being incorporated in the lubricant in an amount less than that normally required fOr' it to function as an extreme pressure agent.v It has been found further that a sulfurized productof oleic acid, which is especially suitable for the purpose of this invention, can be prepared by treating oleic acid with a sulfurizing agent under sulfurizing conditions with a molal ratio of sulfur to oleic acid which is reater than one to one ably less than two to one. I The sulfurized oleic acid may be prepared in accordance with this invention-by reactingoleic acid with free sulfur attemperatures from about- C to 'about'300 C.- Generally, the amount of sulfur used to sulfurize the acidwill be the molal equivalent of the unsaturation of the acid employed. However, the preferred molal ratio of sulfur to acid is from about 1.1 to about 124 (about 12.4% to 16% by weight sulfur based on the oleic acid) Higher ratios may be employed,- but they do-notresult in any appreciable further improvement over that obtained by; using a ratio of about 1.4. Consideration mustj begiven, how: ever, to the fact that with increasing proportions ofsulfur to acid the solubility of the resulting sul; furized-product in mineral oil decreases. The following description of a preferred method used in the preparation of .a sulfuri'zed oleic acid in accordance with this invention is the jpurpos'e of illustrationz "Oleic acid of agood commercial grade was heated in a suitable vessel to a temperature of about-150 C. The heated oleic acid was" blankand prefereted with an inert atmosphere, such as nitrogem natural gas, etc. and then'ff'or each mo'lof oleic acid, about'12 mols of sulfur flowers (correspond; ing to about 13.6% byweight sulfur based on the weight ofioleic, acid) was vadded t0 1 the heated given for treated with an additional 1.0% by weight ot Super Filtrol in the same manner as above and then filtered. The purpose-of 'the clay-treatmentwas to improve the color of thelprodiict' by IQmQY ing color bodies in the sulfurized-material, which bodies appear to have undesirable sludging and corrosive properties. The exact. natumofnsuch.

color bodies is not known, but it would appear.

logical to assume that they comprise substances such as higher molecular weight polymerization products, and the like. 7 I The-rcovered sulfurized oleic acid was a fairly vi'sco usfreddi'sh-yellow colored, clear liquid which way'sufllciently soluble influbricating oil compositi'ons for the purpose of this invention. Analysls indicated a content of chemically combined sum" whicheorresponded' substantially to the suifurconterit of the mixture of oleic acid and suliur 'as mixed; Treatment with a solution of cadmium sulfate to form cadmium sulfide with anyhydrogen sulfide, andth'en with mercury to combine with-any'free (elementary) sulfur iridieated the substantial absence of both elementary sulfur and hydrogen sulfide. 1

The'sulfurized'olei'c acid is incorporated in the lubricating oil base in the form ofthe freeacid. mective-amountsin aturbine oil are in the order elf-020059;, to 0.1% by weight of the-oil, although quantltieso'f between;01% and-020.5% by weight are usually preferred. The small'amount of "sulfurized oleic acid which is suflicient to accomplish the'presentlpurpose is much less: than would be required to alter the other properties of the lubricating composition, including properties. of other additive agentswhich may be incorporated therein; Thus, at the lowconcen'tration of the sulfurized oleic acid used herein the turbine oils, no resistance to extremcipressure wear '(i. e., where. seizure occursl'is-obtaine'd. 9

I-heeffectiveness of sulfurized products of oleic' acid prepared in. accordance'with this invenvolition upon "the antiwear characteristics of turbine oils was determined' byuse of the multiple tour-ban machine similar in principle to the Heel-la eapparatus. described inthepubllcation, Engineering'vol. 136. July l, 1933. .This apparatus eomprises'four steel balls arranged inpyramid formation. The top ball is rotated by spindles against the'thre'efbottom balls whichfa're clamped 1n a' stationary ball holder." The balls are im m'ersedin the oil to be tested.;- Tests were run fon'twoihours atYGQRQ P. under a 14.1.k'i1ogram load and at 85 F. "The diameters of the a scarsfworn on. the. three bal s fo m ns. the base oi the. pyramid, were then measured. and the averagettaken as. thetrueindication oi wear. Results from tests usinga highly refinedturbine. oihcontaining 0.25% by weight of :di-teitiary butyl as an 3 antioxidant and a small but fleetive-amount ofa rust. preventive agent, and tewhieh. was added 010.384; by "weight. basedon the. oil. oi-varioussul'iurized products of-cle'i'c; acid prepared byreacting varying weight ratios of sni'fur and bl'ci'c a'c'idih accordance with the premusi y assented method ofpreparing the sul- The filtrate was then -10.

TABLE I Antiwear properties of turbine oils containing variouasulrurized productsor oleic acid Sulfur Per Cent sampe Ma $01 $8211 832%? of Acid Product inch) (Control: Same oil without sulfurized oleic acid, 22.0 scar diameter in 1/1000 in.)

1 Blend contained only 0.015% ofthesulfurizedproduct.

The results. given inTable I sh w that the. addb tion to the turbine. oil of the: small. proportion o! th sul'iurize'dolei i Products prepared ac. cording totheme'thod. of {this invention reduced. the scar diameters to a value only about one-halt, that. obtained with. the same. oil. but whichou didnot. contain any of the suliurizedoleic. acid. The. results show also. that. the 'rafiQoLsultur toole acid. employed in. the. prenarati'on'oi the. suliurizedfacifd preferably should be not more than about tw mols of sulf r per. mol' of acid. However, the results from using larger ratios show a s b a tial i p vement ov r. the oil containing none. of the sulfurized' oleic acid.

Ol'eic acid was sulfurized with sulfur in a molal ratio of one to one, following the same'procedure as described hereinabove. The results; of antiwear tests similar to those reported in Table I, using the resulting sulfurized oleic acid from a 1:1 mol ratio of sulfur to acid, are given below in Table II. f f

. 7 TABLE I1. Wear evaluation of turbine oils' cont'ainindthe product of sulfurifl'ng'blic acid with sulfur in a mol f0 moZra'tidofmr I 1 Sample No.

Norm: An average total sulfur percentage of 10.2 in sulfurized ofbic acid corresnonds to .21 mol ratioof sulfur to. oleicacid atone to, ope.

The results given 'inTa'ble II demonstrate" the advantage of incorporating in a. lubricating oil a small amount of the suliurized product of olel'e' acidpbta'inedby reacting the 'acid With 'SuHu-r in a'molalra'ti'o clone to one. However, "the data show that, when the mol'al ratiobf sulfur to oleic acid is limited to 1 ml, theph'an'gein the antlwear characteristics ofthe "oil are not as: termined entirely-"by'the amount of thesuliurized product added, but that it is "dependent in some unknown manner 'upon the characterlstlcs'o'fthe. particular sample of 'sulfurized oleic acid" em ployed'., r

The substantial constancy orthe zre'sultsgiven.

in Table I, in contrast to the-variation bribe best results when using sulfurized oleic acid in lubricating oils, the sulfurized acid should be prepared by reacting the oleic acid with more than one molal proportion of sulfur. Furthermore, the improvement in antiwear properties of the oil as evidenced by the comparative scar values, in general, was greater with the sulfurized acids prepared with a mol ratio of sulfur to oleic acid greater than one to one, than the improvement where the ratio was one to one. The results demonstrate, too, that this difference is not attributable to the fact that, with the same weight percentage of sulfurized product, there would be a larger weight percentage of sulfur in the former than in the latter compositions. For example, referring to the data given in Table I, 0.03 wt. of a sulfurized product having a. total sulfur content of 12.8% wt. based on the sulfurized acid (sample No. 1) produced a scar diameter of only 10.7 thousandths of an inch, whereas 0.03% wt. of a sulfurized product containing 25.8% wt. of total sulfur resulted in a scar diameter of 12.5 thousandths of an inch (sample No. 6). Also, it will be noted that 0.015% of the sulfurized acid of sample No. 5 resulted in a smaller scar diameter than 0.03% of the same product (see sample No. 9).

Thus, it is seen that the improvement is not a simple function of the amount of sulfur incorporated in the oil composition. It is evident that the improvement depends upon the form of the sulfur in the sulfurized product, which in turn is dependent, at least partially, upon the ratio of sulfur to acid used in the preparation of the sulfurized acid. Analyses of the various sulfurized oleic acid products indicate that substantially all of the sulfur is in the combined form.

Although it is not fully understod why the sulfurized products containing substantially more than about 10.2% sulfur and obtained by reacting more than one molal proportion of sulfur with one molal proportion of oleic acid are antiwear agents superior to the products obtained by using a molal ratio of unity, it appears that the superiority may be associated with a difference in the molecular species in the products. There is evidence that the superior products contain a substantial proportion of a disulfide of a (ii-acid, that is, a product with a molecular weight twice that of the normal mono-sulfur-oleic acid reaction product whether the mono-product is an epithio type of compound or has some other structure. It is to be understood, however, that the inventon is not to be construed as being limited in any way by any theory as to the explanation of the superior antiwear characteristics of the sulfurized oleic acid prepared in accordance with the present invention and with a sulfur to oleic acid mol ratio greater than unity.

The present invention is directed to the use of a small proportion not greater than 0.1% by weight of sulfurized oleic acid in lubricating oil compositions to improve the antiwear properties of the composition, However, it is contemplated, and it is within the'scope of the invention, to incorporate in the lubricating composition other addtives, such as antioxidants, antifoaming agents, pourpoint depressors, viscosity improvers, rust preventives, and the like. It will be understod, of course, that compounds, such as metallic salts, which react with the sulfurized oleic acid, should be avoided.

The sulfurized oleic acid may be incorporated in lubricating compositions having as base components substances other than mineral oils. Examples of other substances which may be utilized are vegetable oils as castor oil, synthetic lubricants as polymerized propylene oxide, and the like, organic silicones, etc.

Thus, in accordance with the foregoing description of the present invention, an improved lubricating composition may be prepared by incorporating in a lubricating oil a. minor proportion, not greater than 0.1% by weight, of sulfurized oleic acid, andparticularly a sulfurized product of oleic acid prepared by reacting sulfur with oleic acid in a mol ratio of sulfur to oleic acid greater than one to one. The reaction is preferably carried out in an inert atmosphere and the resulting sulfurized product is preferably given a treatment with an adsorbent purifying agent such as filter clay to improve its properties. The sulfurized oleic acid is of utility in lubricating compositions designed for different uses, particular utility being had in connection with turbine oils.

We claim as our invention:

1. A mineral lubricating oil having incorporated therewith from 0.01% to 0.05% of sulfurized oleic acid having a sulfur content of from 12.4% to 25.8%.

2. A turbine oil having incorporated therewith from 0.01% to 0.05% of sulfurized oleic acid hav-- ing a sulfur content of from 12.4% to 25.8%.

3. As an additive for improving the anti-wear properties of turbine oils, a sulfurized oleic acid having a sulfur content from 12.4% to 25.8% said product being substantially non-corrosive.

EMMETT R. BARNUM. GEORGE L. PERRY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,974,299 Churchill Sept. 18, 1934 2,048,479 Adams July 21, 1936 2,062,652 Herrmann Dec. 1, 1936 2,179,063 Smith et a1. Nov. 7, 1939 2,204,538 Lincoln et al. June 11, 1940 2,333,093 Dearborn Nov. 2, 1943 2,402,644 Lazier et a1. June 25, 1946 

